Circuit breaking device



Aug. 24, 1937. FOSTER 2,091,035

CIRCUIT BREAKING DEVICE Filed Jan. 20, I936 BY 6mg); AM; 18

ATTORNEY-S Patented Aug. 24, 1937 UNITED STATES PATENT orricr.

CIRCUIT BREAKING mavror.

New York Application January 20, 1936, Serial No. 59,873

7 Claims.

This invention relates to circuit-breaking devices adapted particularly for use with electrically heated appliances. The-invention is intended especially for use in connection with coffee makers and similar appliances in which water absorbs the heat developed, such as percolators, cookers and the like. It may be employed, however, in connection with any electrically heated appliance wherein it is desirable to break a circult and thereby to discontinue the current upon the attainment of a predetermined temperature.

Heretofore, certain types of electrically heated appliances have been equipped with fuses adapted to melt on the attainment of a definite temperal5 ture, so that the current may be cut off if the appliance is overheated. Such fuses are satisfactory in many instances. They have the disadvantage, however, that the fuse must be replaced after it has melted before the appliance can be used again. Replacement is often a tedious operation which is beyond the skill of the average user. Furthermore, in certain types of appliances such as coffee makers, a fuse cannot be employed satisfactorily. In such apparatus, 25 all of the water is transferred by the application of heat to an upper reservoir, and thereupon the heat must be discontinued. Obviously, if a fuse were used, it would have to be replaced after each successive use of the apparatus.

0 It is the object of the present invention to provide a simple and effective circuit-breaking device which is actuated whenever the temperature rises above a predetermined maximum and which can be re-set readily by a simple manual operation.

Fig. 1 is a vertical section through a portion of 50 an electrically heated coffee maker illustrating the application of the invention thereto;

Fig. 2 is a plan view of the device embodyingthe invention; and

Fig. 3 is a section on the line 3-4 of Fig. 2. 55 Referring to the drawing, I indicates the hous- A further object is the provision of a device of ing of an electric heating element comprising the usual resistance wire 6 wound on a suitable support 1 and connected by conductors 8 and 9 to the source of current through means hereinafter described. It will be understood that the form of the housing element is merely representative of such devices as commonly used in electric heating appliances. The particular form illustrated is adapted for use in the coffee maker or percolator, the base of which is indicated at ill.

The conductor 8 is connected to a bracket ii secured to and insulated from the housing 5 and having a contact l2 thereon. The conductor 9 is connected to a binding post i3 supported in electrically insulated relation to the base I0 which terminates in a projecting prong M. A corresponding prong i5 is connected to a binding post I'B electrically insulated from the base l0 and supporting a resilient arm ll having a contact l8 which is adapted to engage the contact [2 0 when the resilient arm is forced inwardly toward the bracket II.

An electrical insulating block I9 is supported on the end of the resilient arm l1 and a plate 20 is secured thereto with a projecting lip 2|. The plate 20 is electrically insulated from the resilient arm ll by the block l9 which projects into the opening which receives the screw 20'. A nut-2 l and insulating washer 22' secure the screw.

it bracket 22, of heat-sensitive metal, usually designated bimetal and consisting of two strips of metals having different coefficients of expansion rigidly secured together, is mounted on the housing 5; being fastened thereto with screws 23. A screw 24 is mounted in the bracket and engages the housing 5 to afford a degree of adjustment.

A strip'of ordinary resilient metal such as steel 25 having a catch 26 at the end thereof is secured to the bracket 22 and is adapted to engage the lip 2| thereby holding the resilient arm l'l in position to complete the circuit through the contacts l2 and I8. When the device is to be reset, the bimetal element is normally cold (at room temperature) and has resumed its normal position as before heating. The strip 25 then takes the bending stress thereby relieving the bimetal of any strains which might tend to modify its position and the operation of the device.

The bracket of bimetal is adapted to flex under the influence of heat, and as the temperature rises, and particularly when the appliance is overheated, the bimetai will flex sufllciently so as to releasethe catch 26 from the lip 2| when a predetermined temperature is attained. When the lip is released, the resilient arm moves away from the bracket supporting the contact l2, and the circuit is thereby broken. This affords a quick break atthe contact points and reduces arcing when the circuit is broken.

5 To facilitate resetting, a bracket 27 is supported on the housing 5 and carries a pivoted lever 28 having a handle 29 and a free end 30 which is adapted to engage the plate 20. By actuating the lever, the lip 2| may be forced under the catch with the contacts again in engagement.

From the foregoing description, it will be evident that the circuit may be broken automatically and in such a way as to avoid excessive arcing whenever the temperature of the appliance 5 reaches a predetermined point.

Thus, in the coffee maker to which the device is applied byway of illustration, the transferrence of the water to the upper reservoir results immediately in an increase of temperature at the 20 base of the machine because the water is no longer present to absorb the heat. When this condition arises, the flow of current isautomatlcally cut ofi before any damage can result to the heating element. The device may, however, be reset 25 by simply operating the lever, and is again ready for use. Obviously the circuit-breaking device may replace the fuse in any type of electrically heated appliance. v v

\ Various changesmay be made in the details of construction and arrangement of the parts without departing from the invention or sacrificing the advantages thereof. It is intended that all matter contained in the above description or shown in the accompanying drawing shall be in- 35 terpreted as illustrative andnot in a limiting sense. I desire, therefore, that only such limitations shall be placed thereon as are imposed by the prior art.

I claim:

1. In a circuit breaking device for-electrically heated appliances, a fixed contact, a resiliently biased arm having a co-operating contact, a heatsensitive, bimetallic bracket adapted to flex when the temperature rises, and a-resilient detent secured to one arm of the bracket and adapted to engage the arm to hold the contacts in engagement.

2. In a circuit breaking device for electrically heated appliances, a fixed contact, a resiliently biased arm having a co-operating contact, a heatsensltive, bimetallic bracket adapted to flex when the temperature rises, a resilient detent secured to one arm of the bracket and adapted to engage the arm to hold the contacts in engagement, and manually operable means to engage the arm with the detent.

3. In a circuit breaking device for electrically til cured to one arm of the bracket and adapted to engage the arm to hold the contacts in engagement, 8. pivoted lever, one end being adapted to engages the resiliently biased arm and means at the other end to facilitate manual operation of the lever. V

4. In a circuit breaking device for electrically heated appliances, contacts, heat-sensitive means, a resilientdetent supported on the heat sensitive means and adapted to hold the contacts in engagement, the heat sensitive means being adapted to move the detent and to permit separation of the contacts when a predetermined temperature is attained, and means for resetting the detent, the resilience thereof permitting movement independently of the heat sensitive means.

5. In a circuit-breaking device for electrically heated appliances, a fixed contact, an arm having a fixed portion and a movable portion, said movable portion of the arm having a cooperating contact, the movable portion of.said arm being of resilient material biased by the inherent elasticity thereof to move the cooperating contact away from the fixed contact by leverage action due to the movable portion of-the arm fulcruming about the fixed portion thereof, a detent adapted to engage the arm to hold the cooperating contact in electrical. contact with the fixed contact, and heat-sensitive means movable at predetermined temperature to disengage the detent from the arm to permit separation .of said contacts by said leverage action. I

6. In a circuit-breaking device for electrically heated appliances, a fixed contact, an arm having a fixed portion and a movable portion, said movable portion of the arm having a cooperating contact, the movable portion of said am being of resilient material biased by the inherent elasticity thereof to move the cooperating contact away from the fixed contact by leverage action due to the movable portion of the arm fulcruming about the fixed portion thereof, a detent adapted to engage the armto hold the cooperating contact in electrical contact with the fixed contact, heatsensitive means movable at predetermined temperature to disengage the detent from the arm to permit separation of said contacts by said leto one arm at the bracket and adapted to engage the arm to hold the contacts in engagement, and manually-operable means to engage the arm with the detent.

iiGiZT K. FOSTER. 

